1. Field
This disclosure relates to port policy management in a centralized call control packet network, more particularly to managing communications between policy systems and Softswitches/Call Agents to manage calls.
2. Background
Signaling system 7 (SS7) was developed by the International Telecommunications Union (ITU) to specify a protocol for call establishment and teardown from exchange to exchange in a public switched telephone network (PSTN). SS7 is a powerful form of common channel signaling (CCS), which allows information about a phone call to be carried separately from the actual phone call itself. The phone call, comprised of audio signals from one party to another, can be carried on the bearer channel or voice circuit. The signals to establish the call and teardown the call are carried on separate circuits to keep the voice circuits free. This prevents calls that cannot be completed, such as those where the destination phone is busy, from tying up the voice circuits. Other types of call signaling can be used, such as PRI (primary rate interface) and CAS (channel assisted signaling).
With the advent of packet network telephony, where telephone call data is carried across packet networks, such as Internet Protocol (IP) networks, an interface was needed to allow the PSTN system to interface with the data network. These interfaces are often referred to as ‘Softswitches,’ short for software switches. The term ‘call agent’ may also be used and those two terms will be used interchangeable in this discussion. The Softswitch translates the control signals from the PSTN, such as those using SS7 signaling, to the signals used in the packet network, such as IP signaling. Generally, Softswitches are concerned with call control and service intelligence for PSTN and packet networks.
However, as the use of packet networks for telephony has increased, the need for more tightly controlled management of the resources of the telephony network has increased. The wholesalers, the entities that actually own the packet networks, want better control of the network resources in order to provide a legally binding level of service to the providers, who are the entities that offer users' access to the networks. For example, AT&T may own the actual wires across which the data is running, and AOL may provide the users access to the network for Voice over IP phone calls. The dimensions of AOL's access to the circuits may be governed by a service level agreement (SLA) between AOL and AT&T. In addition, AT&T may have other controls it may want to impose on the network, such as the number of users from any provider allowed to access the network from a particular point-of-presence (POP). These policies need to be enforced network wide.
However, currently, most policy systems are based upon dial protocols, such as Remote Authentication Dial-In User Service (RADIUS). The port policy management systems based on RADIUS protocol cannot be used easily by the Softswitch without significant modifications to the call control systems, as Softswitches are designed to handle voice calls, not dial calls. This prevents a network-wide policy enforcement for networks that includes Softswitch based solutions. Further, there are several Softswitch vendors, so it would be desirable to use a standardized form of providing the interface that would allow Softswitches from any vendor to interact with a policy system, based on a protocol that is supported by all the Softswitches in the market place.